Manufacture of transparent fused pure silica



April 22, 1930. H. GEORGE I MANUFACTURE OF TRANSPARENT FUSED PURE SILICA Filed March 9, '1928 //v1 /v folk HzT/VR/ 550/965 4 bis Arrorneys Patented Apr. 22, 19 30 UNI-TED "STATES PATENT OFFICE 111mm GEORGE, oE'rAms, EnANcE, ASSIGNOB To socmTE QUARTZ Simon, or rAms, FRANCE, A COBPOBATIONAOF 'rnANcE MANUFACTURE or TRANSPARENT EUsEn roan SILICA Application filed larch 9, 1928, Serial No. 260,455, and in France larch 28, 1,927.

The present invention has for object an improvement inthe methods of manufacture of transparent fused pure silica in which as primary material there is utilized no longer rockcrystal, -comminuted' or not, but com act .siliceous rocks employed without grin ing up) and in the state of as large blocks as possi le, for'example the special quartzites presenting the following chemical and petrographic characters: high chemical purity, small isometric crystalline elements closepacked without any cement, absence of occluded gases.

The invention relates in particularly to .the method of fusion of the rockswith a view to the cutting up, the selecting and the shaping of the fused blocks.

When proceeding to the fusion of a large block of natural quartzite present' characters previously defined (high chemical purity, small isometric crystalline elements closeacked without any cement, absence of occlu ed gases) it is easily ascertained that however soundthe rock may have appeared, it is comparatively rare that the-whole of the block yieldsafter fusion a block of transparent silica not resenting any defect. Thus are found either slightly coloured regions,for flaws (snows) or bubbles due to local impurities such as a trace of mica. It hasbeen found that these flaws are in general distributed in planes well defined with relation to the primitive rock. The-method of fusion constituting the first phase of the is rendered possible by the high viscosity of fused silica. The operation consists in arranging the blocks in an electric fur nace in the midst ofa mass of .pnre siliceous' ill send, very-carefully packed around them, andv the presentprocess has for its object to obtain the cutting them up along the planes define in roceedin tothe fusion of the whole ou ofblocks and sand. gr p The accompanying drawing represents by way of example a melting furnace adapted for this operation.

cally is a three-phase'furnace. The current leads to the electrodes are marked by the arrows 1, 2 and 3. Thefelectrodesthemselves are represented at c and they are united at the top of the furnace to a piece of graphite (1 serving as neutral point. This arrangement may nevertheless be varied infinitely and the three-phase star connection is represented in this case only as example. It may be advantageous to provide several electrodes per p ase.

In the interior of the cylinder passing through the three electrodes there are arranged the largestblocks of rock 6. For example with a furnace of centimetres diameter and 1, 5 metres hi b, there .can be arranged in the axis bloc weighing 5 to 10 kilo ams. Externallyof the cylinder passilig t ough the electrodes, there are arranged smaller blocks. In proportion as' the blocks are arran ed in the furnace, sand is carefully pac ed around them. The mounting of the furnace being finished, orieprocee to the fusion and obtains a composite ingot, the contour of which is for example the line f. Fusion being completed, the furnace is taken down and the ingot allowed to cool.

The second phase of the process consists in dividing u this ingot by mechanical means of anykin in order'to be able to examine the fused blocks and to divide them up in their turn with elimination of blemished partsi the flaws. The sound ieces are then examined from the point 0 view of their trans The metal sheath a serves as casing for the I parency and their optical qualities. The finer ones may be utilized for optical puroses and they are further out or brought -1I1t0 .shape and polished. Those which do not present optical homogeneity are brought into shape or again treated by drawing according to the arrangements of the French name to this specification.

Patent No. 585,214, dated 2nd November 1923, and the application for patent filed on 4th May 1926 for Process and arrangement for the drawing of articles in silica lass or any other vitreous material, or again y hotstamping according to the application for patent filed on 6th January 1927 for Process and apparatus for hot-stampin of articles of fused silica and novel artic es resulting therefrom, or by mechanical working according to the French Patent No. 601,543, dated 30th October 1924.

.What I claim is.

1. A process for the manufacture of transparent, fused, pure silica, consisting in carefully packing a mass of silicious sand around as large blocks as possible of uartzites, said blocks having a high chemica purity, small isometric crystalline elements close packed without any cement and without any occluded gases, in melting said blocks and siliceous sand, and after cooling, in dividing up the composite ingot obtained along the planes containing the flaws orbubbles arising from local impurities. for the purpose described.

2. A process for the manufacture of transparent, fused, pure silica, consisting in carefully packm a mass of-.s1l1c1ous sand aroundas large bloc s as possible of quartzites, said blocks having a high chemical purity, small isometric crystalline elements close packed without any cement and without any occluded gases, in melting said blocks and siliceous sand, and after cooling, in dividing up the composite ingot obtained along the planes containing the flaws or bubbles arising from local impurities, and bringing into shape the pieces thus" obtained.

In testimony whereof I have signed my HENRI GEORGE. 

